For an assignment this term I have to come up with an anti-cliché superhero. I am going to do a superhero that changes shape from thin to big and was wondering if anyone knew a word for this change of shape/size.

Mutilate is. I meant to keep that mutilate. Mutate refers to changing oneself... you can't mutate something else, can you? And I see that mutate can be used transitively... can you give an example? I couldn't think of any.
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asymptoticallyJul 23 '12 at 11:03

1

I would suggest "transmute" over "mutate" in this context.
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crisis.sheepJul 23 '12 at 11:04

Your superhero appears to be changing from an ectomorph to an endomorph, so you could do something based on that.

Endomorpher? Endomorpho?

To answer the more general aspects of your question, the basic term for changing shape is metamorphosis. Which also means that names based on the body types noted above have a useful intrinsic allusion in place.